Synthesize radioactive retinoids for use as tracers in metabolic studies, both in vivo and in vitro. The approach will involve the synthesis of small quantities of several different retinoids, the choice of which will be dictated by the needs and interest of the NCI Carcinogenesis Program, In general, the contractor will: synthesize a variety of radioactive retinoids; provide assay and analytical data on all compounds; store, package, and distribute all compounds; maintain an accurate inventory of compounds; and prepare sheets describing preparative methods and requirements for handling and storing materials.